Feed control device for drilling rig drums



v -dl May 8, 1962 J. H. WILSON FEED CONTROL DEVICE FOR DRILLING RIG DRUMS Original Filed Oct. 24, 1957 5 Sheets-Sheet l INVENTOR. JUHN HART WIL SUN HIE HEENT May 8, 1962 J. H. WILSON 3,033,530

FEED CONTROL DEVICE FOR DRILLING RIG DRUMS Original Filed Oct. 24, 1957 5 Sheets-Sheet 2 INVENTOR. JUHN HART WIL SUN H15 HGENT y 8, 1962 J. H. WILSON 3,033,530

FEED CONTROL DEVICE FOR DRILLING RIG DRUMS Original Filed Oct. 24, 1957 5 Sheets-Sheet 3 INVENTOR. JUHN HA5 T WIL SUN M HEEVT y 8, 1962 J. H. WILSON 3,033,530

EEED CONTROL DEVICE FOR DRILLING RIG DRUMS Original Filed Oct. 24, 1957 5 Sheets-Sheet 4 INVENTOR. JUHN HART WILBUN y 1962 J. H. WILSON 3,033,530

FEED CONTROL DEVICE FOR DRILLING RIG DRUMS Original Filed Oct. 24, 1957 5 Sheets-Sh t 5 INVENTOR JOHN HART WILSON United States Patent Ofitice 3,633,530 Patented May 8, 1962 3,033,530 FEED COOL DEVICE FUR DRILLING RIG DRUMS .lohn Hart Wilson, R0. Box 1031, Wichita Falls, Tex. Continuation of application Ser. No. 692,130, Oct. 24, 1957. This application May 22, 1961, Ser. No. 116,911 Claims. 7 ((11. 254-173) This application is a continuation application of Serial Number 692,130, filed October 24, 1957, now abandoned.

This invention relates to a feed control device for drilling rig hoist drums, such as used on rotary drilling rigs.

Heretofore, the feed-oil of a drilling line from a hoist of a drilling rig was normally left to the judgment of the individual driller, and if the driller was impatient, or the line was fed off too fast, the result frequently was the sticking of the drilling bit, with the drill stem frequently being twisted in two, however, an overcautious driller, who hesitated to let the drill line off as rapidly as the bit could drill the formation, could materially retard the drilling operation.

The present invention is designed to keep a predetermined amount of weight on the drill bit, and if the formation being drilled cuts easily, the drilling line will feed off as rapidly as the bit will drill the formation, but, if the progress of the drilling is retarded, due to hard formation, the drilling line will not be fed off the drum with sufiicient rapidity to cause the bit to become stuck.

Various attempts have been made heretofore to con trol the feed-off of line from drums, however, these devices for the most part, were too complex and bulky and required such excessive maintenance as to make their use impractical in oil field drilling.

The present device is so constructed, that once it is set to operate under predetermined conditions, it requires little or no attention, so long as the drilling operation is progressing in a uniform manner.

An object of this invention is to provide a feed control device for the hoisting drums of drilling rigs, which device is sensitive to the change in weight of the string of drill stem, and which will feed cable off the hoisting drum at a rate commensurate with the change in weight on the drilling bit. I

Another object of the invention is to provide a feed control device for the drum of a rotary drilling rig, whereby the drilling line will be fed off in accordance with the weight being maintained on the drill bit and which will limit the rate of feed-off of the drilling line, in event the drill bit should suddenly drop into a cavity or drill into a soft, mushy formation.

Still another object of the invention is to provide a feed control device for drilling rig drums which will auto matically release, when taking up the empty blocks, thereby minimizing wear on the feed control unit.

Yet another object of the invention is to provide a feed control unit for drilling rig drums which has a minimum of working parts, yet which is sensitive to small changes in the load so that uniform weight can be maintained on the drill bit at all times.

A still further object of the invention is to provide a feed control device for drilling rig drums which is simple in construction, low in cost, easy and effective in operation, and which requires a minimum of maintenance.

With these objects in mind and others which will become manifest as the description proceeds, reference is to be had to the accompanying drawings, in which like reference characters designate like parts in the several views therein, in which:

FIG. 1 is a fragmentary, top plan view of a drilling rig hoisting drum, showing the feed control device attached thereto;

- FIG. 2 is a vertical sectional view taken on the line 22 of FIG. 1, looking in the direction indicated by the arrows;

FIG. 3 is a sectional view taken on the line 3-3 of FIG. 2, looking in the direction indicated by the arrows; and showing the drive and braking mechanism of the feed control unit;

FIG. 4 is a diagrammatic view of the air control system of the feed control device;

PEG. 5 is a diagrammatic view of the hydraulic system used in connection with the feed control device; and

FIG. 6 is a diagrammatic, elevational view of a typical derrick construction, showing blocks, a Kelly joint, and drill stem as used in a drilling operation in a well.

With more detailed reference to the drawing, the numeral l. designates generally the draw works of a drilling rig, which unit has sills or frame 2, and a hoisting drum 4, which hoisting drum is mounted on a shaft for rotation of the drum 4- about its axis. It is the usual practice to have a high speed clutch 8 connected to the drum shaft d at one end of the drum in driving relation therewith, and a low speed clutch 10 connected to the drum shaft 6 at the other end of the drum 4 in driving relation therewith. An over-running clutch 12 is provided within the drive system, intermediate the high speed. clutch 8 and the hydromatic brake 14. The clutches 8 and 10 are of the pneumatic type and are supplied with air through conduits 16 and 18, respectively, which conduits lead through a rotary fluid seal 20, in a manner well understood in the art.

Conduits (not shown) convey the pneumatic pressure from the rotary seal 20, on the outer end of shaft 32 of the hydromatic brake 14, to the respective clutches 8 and 10, through hollow shafts and other conduits, as is well understood in the art of neumatics.

The drum 4 is usually driven'by roller drive chains 22 and 24, which pass around sprockets 26 and 28, respectively, which sprockets are journaled on drum shaft 6, and around complementary sprockets (not shown) on counter shafts, transmissions or the like, to drive the drum in a manner well understood in the art of drilling. A sprocket Si is mounted on shaft 32 which shaft 32 is in axially aligned relation with drum shaft 6. A chain 34- surrounds sprocket 36* and sprocket 36, on feed control shaft 38.- The feed control shaft 33 is mounted within the feed control device which is designated generally by the numeral 4%. The shaft 38 has asprocket 42 journaled thereon for turning movement about the shaft. The sprocket 42 has clutch jaw teeth 44 thereon, which teeth extend outward therefrom. A sliding clutch 46 is splined to shaft 38 so as to complementally engage jaws 44 on sprocket 42, when in one position, and to disengage the jaws 44, when in another position.

A drive chain Stl passes around sprocket 42 and around sprocket 52, so as to connect shaft 38 in driving relation with shaft 54. The sprocket 52 is secured to shaft 54 and upon rotation of shaft 54, sprockets 52 and 56, the sprocket 56 also being secured to shaft 54, will be rotated therewith.

On the opposite end of shaft 54 from the sprocket 56, is an air actuated brake, which is generally designated by the numeral 58, as will best be seen in FIGS. 2 and 3. The brake 58 is controlled by air pressure which is applied through conduit 122 from a remote point, as will be explained in detail hereinafter.

The air actuated brake 58 has a toothed hub 62 therein, which toothed hub is mounted on and secured to the shaft 54. The toothed hub 62 engages the inner teeth of plates 64 within brake 58. A plurality of friction disc elements 66 are provided, which elements have peripheral teeth, which teeth engage complementary teeth 68 around 3 the inner diameter of cylindrical shell 70 of the brake element 58.

An annular disc 72 is positioned against the outermost of the friction elements 66, which annular disc is made of a heat resistant material, such as molded asbestos or the like, and is ribbed to minimize the transfer of heat and to permit air to circulate therethrough. An elastomer pressure tube 74, which is axially expansible, is positioned within the cylindrical casing 71 of the brake element 58, and is in abutting relation with end member 76, which end member 76 is secured to cylindrical casing 713 by means of cap screws 78. The other end of the cylindrical casing 70 is closed by an end member 86, which is socured thereto by means of cap screws 32. The end member 89 is also secured to the stationary gear reduction housing 84 by means of cap screws 36, which housing is rigidly secured to frame 2.

With the friction elements 66 being connected to the cylindrical casing 79 and to the gear reduction housing 84 through teeth 68, and with the plates 64 connected to shaft 54 through toothed hub 62, it will be seen that, upon application of pressure by axially expansible tube 74, the plates 64 and 66 will be brought into frictional engagement, and that the frictional engagement will be proportionate to the amount of pressure which is applied to the tube 74 through air conduit 122. The shafts 38 and 54 are journaled on bearings 39 in gear housing 84, and on bearings 45 therein, to make possible the free rotation of these shafts, respectively.

A sprocket and chain housing 88 is mounted adjacent housing 84, and is rigidly connected therewith and extends thereabove. A hydraulic pump 90 is mounted near the upper end of housing 88 and has a sprocket 92 thereon, which sprocket 92 on pump shaft 93 is in aligned, driving relation with the sprocket 56 on shaft 54. A chain 94 passes around sprockets 5.6 and 92, so as to couple the pump 90 in driven relation with the shafts 54 and 38..

The hydraulic pump 90 has an intake pipe 96 extending into hydraulic fluid reservoir 98. A filter screen 100 is shown in the intake pipe 96, just inside the reservoir 98, and a discharge pipe 1&2 leads from the hydraulic pump 90 to a pressure relief valve 104, with another discharge pipe 106 leading from pipe 162 through metering valve 108, which metering valve 103 may be of the manually operated globe or needle type, or it may be of the remote controlled type, so that the discharge of fluid therethrough, from the hydraulic pump 90, may be accurately adjusted. A by-pass 1110 leads from the relief valve 104 into discharge pipe 1117 at a point between the metering valve 108 and the discharge outlet 112 in the reservoir 93. The pressure relief valve 104 in pipe 1% is set to discharge into pipe 110 at a given pressure, however, if the restriction in the metering valve 108, in pipe 196, causes the pressure to exceed the predetermined setting, the excess pressure fluid will be by-passed through by-pass pipe 110 into discharge pipe 167 and back into reservoir 98 through discharge opening 112. In this manner an accurate maximum setting for the speed of the pump can be made and accurately controlled, thereby controlling the maximum speed of rotation of the drum, due to the pressure of fluid constrained within the pump, and to the chain and sprocket drive. This arrangement will prevent a sudden lowering of the drill pipe, in event an unusually soft formation, or a cavity in the formation is encountered, as will be more fully brought out hereinafter.

An air supply pipe 114, connected to a suitable source of high pressure air, not shown, passes through air pressure regulator valve 116 and which air supply pipe 114 has a pressure gauge 118 therein, from which the pressure of the incoming regulated air may be determined. The air supply line 114 leads to an inverse pressure relay 120, which may be so regulated as to maintain a given pressure in pipe 122 which leads to the air actuated brake, which brake is generally designated at 58.

A gauge protector valve 128 is provided in the fluid loaded pipe 146, intermediate the sensator diaphragm member 132 and the inverse relay 126. The purpose of the valve is to reduce or cut off excessive pressure generated by the sensator diaphragm member from the inverse pressure relay 120. The valve 128 is of the type which is commonly used as gauge protectors to prevent damage to the sensitive members in gauges and instruments such as diaphragms, within the inverse pressure relay 120.

A pressure gauge 124i is positioned within pipe 122 to determine the correct pressure to be maintained on pipe 122, and on expansible tube 74. The fluid loaded pipe 146 leads from inverse pressure relay 12% through the pressure protector valve 12%, valve 144 and through T 139 to sensator diaphragm member 132 connected to fluid loaded pipe 146. The pipe 146 is preferably filled with low expansion, low freezing liquid, so it will react accurately to the inverse relay 1211, upon movement of the sensator diaphragm member 132.

The sensator diaphragm member 132 is pivotally connected, at one side, to an arm 134 and to a lever 136 on the opposite side. A winding drum 138 has several turns of cable 142 thereon, one end of which cable is indicated at 142 and extends upward into the derrick and over the crown block sheaves, to form a dead line. The other end 142a of the cable 142 is anchored to lever 136, so as to impart movement to the lever 136, which movement will be proportionate to the amount of pull that is being imparted to the cable. The sensator diaphragm member 132 is connected intermediate lever 136 and arm 134, so as to react to the pull on cable 142. The pipe 146 leads from sensator diaphragm member 132 and connects to the inverse pressure relay and to a pipe 148 leading to a weight indicator 15%. The sensator diaphragm rnemher 132 is sensitive to pull applied to the cable and transmits pressure to the weight indicator and to the inverse pressure relay 120 proportionate to the pull. A valve 144 is provided within pipe 146 to enable the closing of the conduit between inverse pressure relay 1% and the diaphragm 132, which renders the brake 58 inoperative, yet permits the weight indicator to function in the same manner as if the feed control unit was not connected thereto. A pipe 148 leads from the other end of T 131), and extends to weight indicator 150 which is connected within fluid loaded pipe system 146148.

Operation In the drilling of deep wells, such as oil wells and the like, various earth formations are encountered, some of which drill easily, and in some of which drilling is very difiicult, and frequently crevices, caverns, and the like are encountered, into which the drill stem will suddenly drop, if not retarded. The rotary table will rotate the drill stem with the drill stem furnishing the weight, whereby the bit will cut into the earth formation. However, as more drill stem is added, the weight on the bit becomes excessive, so some of the load is sustained by a block and tackle arrangement, which is connected between the top and the derrick D and the rotating swivel joint on the upper end of the Kelly joint K to which the drill stem S is connected. The Kelly joint is suspended from the block B of the block and tackle. The end 142]) of the cable of the block and tackle arrangement is wound onto a drilling rig hoist drum 4, which drum is provided with brakes and is usually provided with a hydraulic retarder brake, which is usually known as a hydromatic brake. It is the drillers responsibility, however, to see that the cable is fed-cit the drilling rig hoist drum as fast as possible, consistent with the correct load weight on the drilling bit C which extends into the well or bore W at the lower end of the drill stem S. It is to the end of eliminating the uncertain human element, that the present device was designed.

Since rotary drilling rigs must frequently be moved from place to place, it is most desirable to keep all the accessories and attachments thereto toa minimum in weight and bulk, to enable ready transportation thereof, and while other cable feeding control devices have been proposed heretofore, these were so bulky, heavy, and expensive that many operators were reluctant to use such devices, furthermore, other weight indicating devices are insensitive to slight changes in weight and are com iicated in structure.

, The present device is comparatively light in weight, and so simple in construction as to be readily attached to the hoist drum of most rotary drilling rigs, and can be utilized therewith to maintain even weight on the drill bit, and which device is sensitive to the slightest change in weight brought about during the cutting of the bit into the formation.

In raising the drill stem out of the hole, it is desirable to raise it as rapidly as possible, but when it goes into the hole or well, it is desirable to retard the speed of the downward movement thereof. In coming out of the hole an over-running clutch mechanism 12, which is connected to the drum 4, it so arranged that, when the drum 4 is rotated in one direction, the elements in the over-running clutch 12 will not engage, thereby rendering the hydraulic retarder 14 immobile. This enables the hoisting of the drill stem as rapidly as desired without the hydraulic retarder 14 interfering with the turning of the drum 4. To return the empty blocks quickly, a jaw clutch 11 may be utilized, if desired, to disconnect the over-running clutch unit 12 and the hydraulic retarder brake 14. However, in the lowering of drill stem into the hole, it is desirable to engage the clutch 11, the over-running clutch 12 will then engage to rotate shaft 32 and an impeller within the hydraulic retarder 14, which retards the descent of the drill stem, thereby enabling maximum safety in going into the hole with the drill stem.

However, once-the drill bit is on the bottom of the hole, and the drilling is ready to progress, the drill stem is lifted clear of the bottom of the hole, and the weight of the load on the block is read from gauge hand 152 on weight indicator 150. The weight indicator is usually calibrated in thousands of pounds and is conventional, and is used on practically all drilling rigs.

Once the weight of the drill stem is determined, which is known as the block load, the indicator hand 154, which indicates the weight on the drill bit, is set at zero, then as the cable on the drum 4 is slackened, the indicator hand 152, which indicates the block load, will drop back to a lesser reading, with the indicator hand 154, which indicates the weight on the drill bit, showing increased weight thereon proportionate to the weight reduction on the block load, with the sum total of the two weights thus indicated by the hands 154 and 152 equaling the total load at all times. The weight indicator 150 is of conventional design and is only described as aiding in the accurate setting of the inverse pressure relay, in connection with the system.

Different formation and different types of bits require difierent weights for the best cutting action thereof, and also for the longest cutting life of the bit. With these factors having been previously determined, the driller knows how much weight should be placed on the bit. It is at this stage of the drilling that the feed control device is put into automatic operation.

The cable anchor, designated generally by the numeral 133, is so designed that, when the dead line cable 142 is passed around the drum 13S and the lever 136 is clamped to the end 142a of the cable 142, the cable 142 is secured against lineal movement. Upon application of a pull load on cable 142, movement will be accorded to lever 136 relative to arm 134, whereupon, a sensator diaphragm member 132 will be moved. With a chamber in the sensator diaphragm 132 filled with liquid, and with the pipes 146 and 148 filled with liquid, any movement of the lever 136 will cause pressure on the diaphragm in such manner that the liquid reaction in pipes 146 and 148 will act upon the pressure sensitive elements in the inverse relay 120 and in the pressure sensitive elements in the weight indicator 150, and with the correct weight or load on the drill hit, an adjustment knob 121 may he moved to adjust the elements in inverse relay 120, whereby, as the drill bit drills into the formation and the pressure thereon is relieved, which will cause greater weight on cable 142, which will increase the pressure in pipes 146 and 148, and since the pipe 146 connects with inverse pressure relay 1211, in a manner well understood in the art of pressure elements, the increase in pressure on an element in inverse pressure relay 120 will cause a proportionate closing of a Valve therein, so air under pressure will be passed from air pressure supply pipe 114 through regulator valve 116, through inverse pressure relay 120 at a lower pressure into pipe 122. Upon lowering the pressure in pipe 122, which leads to pressure actuated brake 58, the axially expansible air tube 74 will yield to permit relative slippage between the brake plate 64, which engages shaft 54, and the brake friction element 66, which is engaged with .cylindrical casing 70. As the weight on the cable 142 becomes less, the pressure in the sensator diaphragm member 132 becomes less, and since the hydraulic pressure within the pipe system 146-148 will equalize, thereby lessening the pressure on a pressure sensitive element in inverse pressure relay 126, the valve will be opened, which will permit air under increased pressure, to pass through pipe 122 into axially expansible tube 74, so as to retard the feed-off of the cable, so as to maintain a uniform weight on the V drilling bit.

The inverse pressure relay 1 20 is of the character which utilizes the bleeding of a small amount of air therefrom, which enables inverse pressure relay to function at all pressures, within the range limits thereof.

So long as the drilling continues in normal formation, the brake 58 will maintain a uniform pressure on the friction elements 64 and '66 in brake 58, thereby retarding rotation of shaft 54 in proportion to this pressure. The shaft 54 is provided with sprockets 52 and 56 thereon. The sprocket 5 2 is connected in geared reduction through chain 50 with sprocket 42, which sprocket 42 is journaled on shaft 38. The sprocket 42 has clutch teeth 44 thereon, which teeth are engageable with teeth on clutch 46, which clutch 46 is secured against relative rotation on shaft 38, and with the teeth of the clutches engaged, and with a sprocket 36 connected in gear reduction relation through chain 34, with a sprocket 38 on shaft 32, which shaft 32 is connected in driving relation with drum 4, it will thus be seen, that by maintaining shaft 54 against movement by the utilization of brake 58, the drum 4 will be held against movement, or will be permitted to feedoif at a rate proportionate to the slipping of the friction elements 64 and 66 in brake '53. 'In this manner a uniform control of the feed-off of the cable from the drum may be had. i

If, during the course of drilling, the drill bit drills into a cavern, which would normally let the drill stem drop, or into a soft formation which will not sustain the weight of the drill stem, a further device is provided to limit the maximum rate of downward movement of the drill stem, either as a free falling object or as a drill stem, with the drill bit thereon drilling into the soft formation, which formation will not sustain the load weight on the bit.

A hydraulic system is provided for the feed control device, whereby a hydraulic pump 90, which is preferably of the vane type, is connected in geared relation'by means of sprockets 56 and 92 through a chain 24 to shaft 54, and through geared reduction of sprockets and chains, to shaft 32, which in turn, interconnects with the drum 4. The'pump 91} is of the type which will withdraw hydraulic fluid through filter screen 100, through suction pipe 96 and discharge the fluid, under pressure, outward '2 through pipe 1&2, and with the pressure relief valve 184 connected to pipe 102, and with pipe 1% leading from relief valve 1&4 through metering control valve 198 to discharge through opening 112 into reservoir 93, the device is ready to operate.

The metering valve 1% is connected to pipe 162 and to pipe 106, and is provided with a hand wheel Hi9 so as to enable the restriction of flow therethrough into pipe 166, which restriction likewise retards the rotation of the rotating elements in the pump 9%). However, a bypass conduit is provided from relief valve find to connect with 136 intermediate the metering valve 1% and the reservoir 93. Therefore, if the flow of fluid through pipe 192 exceeds the predetermined pressure setting of valve 108, the excess fluid will be by-passed through by-pass conduit 11d into reservoir 98. By retarding the rotation of the hydraulic pump 9% the maximum rotation of shaft 54 is predetermined, which insures maximum rotation of the winding drum 4, thereby preventing the sudden dropping of the drill stem into a cavity, or permitting it to feed off too rapidly into a soft, gummy formation in which the drill stem might be twisted in two.

It will be readily appreciated that the maximum rate of rotation of the hoisting drum 4 can be readily and easily set by manually closing valve 108, while the blocks are near the top of the derrick, then by opening valve 108 to permit the flow of liquid therethrough, the shaft 9-3 of the pump 99 will be permitted to rotate at a retarded rate of speed, and since the shaft of the drum 4 is in geared relation to the hydraulic pump 99, the rate of rotation of the drum 4 and the rate of descent of the drill stem, which is suspended by the blocks in the derrick, can be so regulated as to give the maximum rate of travel of the drill stem in event the drill stem should encounter a cavity or formation too soft to sustain the weight of the drill stem.

The rate of feed-off of the cable can be readily set so as to maintain a given load on the bit by the adjustment of regulator wheel 121 on inverse pressure relay 120.

The cable 142 is anchored against lineal movement, and is also anchored to lever 136 in such manner as to impart a relative movement to the lever 136 with respect to the arm 134, when pull is exerted on dead line cable 142, which pull will transmit reactionary pressure from sensator diaphragm member 132 to and through pipes 146 and 148 to inverse pressure relay 126 and to weight indicator 159. The weight indicator 1% is of conventional type, and preferably has two hands thereon, one hand 152, which indicates the full block load of the amount of drill stem being handled by the blocks, and the other hand 154 will indicate the actual weight on the drill bit.

A pressure control wheel 21 is provided on pressure relay 120, which enables the setting of the pressure relay at a pressure to permit the brake 58 to slip to feed-off cable, when the weight on the bit becomes less than the predetermined setting of the pressure relay as determined by the pressure control wheel 121 on relay 12%.

The setting of the inverse pressure relay 120 may be readily accomplished by regulating the wheel 121 until there is no slipping of brake 58, whereupon, the pressure control wheel-may be moved in one direction or the other until slippage occurs at the desired weight on the bit. This setting will maintain a constant weight on the bit, regardless of the speed of drilling, so long as the bit does not run into a cavity or into formation too soft to sustain the weight of the drill stem.

Having thus described the invention, what is claimed is:

1. In a feed control device for a rotary drilling rig, which rig has a hoisting drum for taking in and feeding out a terminal cable which is wound around said drum and which cable is adapted to support the weight of the drill pipe, an air actuated brake connected in braking rela- 8 tion with said drum and having a cable tension measuring device employing a liquid body under pressure proportioned to the cable tension, the improvement'comprising; in combination, means communicating with said brake for supplying pressurized actuating air thereto, an inverse pressure control valve operatively associated with said brake for controlling the pressure of said actuating air within said brake, said tension measuring device being connected in controlling relation to said inverse pressure control valve for causing said inverse pressure control valve to vary the pressure of said actuating air to variations in the cable tension, a hydraulic pump connected in driven relation with said hoisting drum, and means defining a hydraulic fluid circuit through said pump, said circuit including a constriction on the delivery side of said pump whereby said pump will limit the rate of rotation of said drum incident to the unwinding action of said cable when said brake is released.

'2. In a feed control device for a rotary drilling ri the rig having a hoisting drum for taking in and feeding out a terminalcable wound around said drum, an air pressure actuated brake connected in braking relation with said drum, and having a cable tension measuring device employing a liquid body under pressure proportioned to the cable tension, the improvement comprising; in combination, an air supply pipe-communicating with said brake for supplying actuating pressurized air thereto, an inverse pressure control valve in said pipe regu lating the pressure of air within said brake, said inverse pressure control valve being operatively connected to said measuring device and being controlled thereby to vary the air pressure Within said brake inversely with respect to variations in said cable tension, a hydraulic r'etarder pump connected in geared, retarding relation with said drum, means restricting the discharge of hydraulic fluid from said hydraulic retarderpump in proportion to the increase in speed or rotation of said drum due to the decrease of tension on said cable by the release of said brake.

3. In a feed control device for maintaining a given pull on a cable wound on a hoisting drum, an air actuated brake connected in braking relation with said hoisting drum, an air supply pipe operably connected to said brake, an inverse pressure control valve within said air supply line, a liquid pressure sensating element operably connected to the weight load of said hoisting drum, a pipe leading from said pressure sensating element to said inverse pressure control valve in said air supply pipe, said liquid pressure sensating element and said sensating pipe connected thereto being preloaded with a liquid to transmit pressure from said pressure sensating element to said inverse pressure control valve, said inverse pressure control valve being responsive to liquid under pressure in said pressure sensating element so as to direct air at an inverse pressure from said air supply pipe to said air actuated brake, a hydraulic pump connccted in geared relation with said hoisting drum, a hydraulic fluid reservoir, a pipe connected to the suction side of said pump and being in fluid communication with said hydraulic fluid reservoir for directing hydraulic fluid to said pump, a discharge pipe connected to said pump and leading to said hydraulic fluid reservoir, said discharge pipe having an adjustable restriction formed therein intermediate said pump and said hydraulic fluid reservoir, which hydraulic pump, when rotated by said drum, forms a retarding element to retard the rotation of said hoisting drum when thevpressure in the pipe preloaded with liquid has been relieved of pressure by the liquid pressure sensating element to such extent that said fluid actuated brake does not retard the hoisting drum from rotating in excess of the setting of said restriction in the discharge line leading from said pump to said hydraulic fluid reservoir.

4. A feed control device for a drilling rig, said feed control device comprising a hoisting drum, a chain gear reduction unit connected in driven relation with said hoisting drum, said chain gear reduction unit having a I driven shaft, a fluid actuated brake on said driven shaft of said gear reduction unit, a hydraulic pump retarder mechanism connected in driven relation to said hoisting drum through said gear reduction unit, a hydraulic fluid reservoir, a suction pipe leading from said hydraulic fluid reservoir to the suction inlet of said pump retarder mechanism, a discharge pipe leading from the outlet of said pump retarder mechanism to said hydraulic fluid reservoir, a restrictive control valve in said discharge pipe intermediate said hydraulic pump retarder mechanism and said hydraulic fluid reservoir, a by-pass relief valve in said discharge pipe and connected in parallel relation to said restrictive control valve, which by-pass Valve is set to by-pass hydraulic fluid into said reservoir when the pressure exceeds the setting of said relief valve, a fluid pressure line connected to said fluid actuated brake, an inverse pressure relay valve within said line leading to said fluid actuated brake, a pressure sensator, and a cable leading from said hoisting drum and being connected in operative relation with said pressure sensator, so upon movement of said pressure sensator, fluid pressure will be transmitted through said pipe leading to said inverse pressure relay valve, said fluid actuated brake being connected with said sensator by said inverse pressure relay valve in such manner that pressure on the fluid actuated brake will be decreased by an increased tension on said cable and increased by a decrease in tension on said cable.

5. A feed control device for drilling rig hoisting drums, which device normally controls the feeding of the drill pipe into the bore hole of a well in accordance with the predetermined weight on the drill bit, the formation in said bore hole at least partially supporting the weight of said drill pipe and said drill bit, and for retarding the descent of said drill pipe in said bore hole beyond a predetermined rate when the support of the drill pipe and the drill bit by the formation becomes less than a predetermined setting of the retarder to the feed control device, which feed control device comprises, in combination with a drilling rig hoisting drum having a cable spooled thereon; an air actuated brake, a pressure sensating element operably connected to the weight load supported by said drilling rig hoisting drum, an air supply conduit, an inverse pressure control valve within said air pressure supply conduit and being intermediate said source of air pressure supply and said air actuated brake, a liquid loaded pipe leading from said pressure sensating element to said inverse pressure control valve so upon increase of pressure on said liquid loaded pipe by said pressure sensating element, said inverse pressure control valve will close in proportion to the increase in pressure in said liquid loaded pipe, which will decrease 'air pressure to said air actuated brake such proportionate amount, a hydraulic fluid reservoir, a positive displacement pump, a conduit leading from said hydraulic fluid reservoir to the inlet side of said pump and being in communication with said hydraulic fluid reservoir, a discharge conduit leading from the outlet side of said positive displacement pump to said reservoir, a manually controlled valve within said discharge pipe leading from said positive displacement pump to said reservoir, said air actuated brake and said positive displacement hydraulc pump'being operably connected to said drilling rig hoisting drum so upon a decrease of the load on said hoisting drum, said air actuated brake will release, and upon decrease of the load on said hoisting drum beyond a certain predetermined setting of said manually controlled valve in said discharge line, said manually controlled valve will impinge hydraulic fluid being pumped through said discharge line by said positive displacement hydraulic pump to retard the rotation of said pump and said drilling rig hoisting drum.

References Cited in the file of this patent UNITED STATES PATENTS 

